Problem 6.300

$6.300 .$ A $\Sigma^{+}$ hyperon with kinetic energy $T_{\Sigma}=320 \mathrm{MeV}$ disintegrated during its flight into a neutral particle and a positive pion outgoing with kinetic energy $T_{\pi}=42 \mathrm{MeV}$ at right angles to the hyperon's motion direction. Find the rest mass of the neutral particle (in MeV units).

m=\sqrt{m_{\Sigma}^{2}+m_{\pi}^{2}-2\left(m_{\Sigma}+T_{\Sigma}\right)\left(m_{\pi}+T_{\pi}\right)}=0.94 \mathrm{GeV} \text{neutron}

Elementary Particles